Saint Mo Chutu mac Fínaill (died 639),[1] also known as Carthach or Carthach the Younger (a name Latinized as Carthagus and Anglicized as Carthage),[2][3] was abbot of Rahan (Irish Rathan), Co. Offaly, and subsequently, founder and first abbot of Lismore (Irish Les Mór Mo Chutu), Co. Waterford.[4] The saint's Life has come down in several Irish and Latin recensions, which appear to derive from a Latin original written in the 11th or 12th century.[4]

Mo Chutu first became abbot of Rahan, a monastery which lay in the territory of the southern Uí Néill. He composed a rule for his monks, an Irish metrical poem of 580 lines, divided into nine separate sections, a notable literary relic of the early Irish Church.[2]

According to the Annals of Ulster, he was expelled from the monastery during the Easter season of 637. The incident has been connected with the Easter controversy, in which Irish churches were involved during the 7th century. Through his training in Munster, Mo Chutu may have been a supporter of the Roman system of calculation, which would have brought him into conflict with adherents of the 'Celtic' reckoning in Leinster.[4]

St. Carthage's cathedral in Lismore

Following his expulsion, Mo Chutu journeyed to the Déisi, where he founded the great monastery of Lismore (in modern County Waterford). The Latin and Irish Lives make very little of Mo Chutu's earlier misfortune and focus instead on the saint's resistance against the oppressions of Uí Néill rulers and by contrast, his joyous reception among the Déisi.[4] Mo Chutu is also portrayed in a heroic light in an Irish saga entitled Indarba Mo Chutu a r-Raithin ("The expulsion of Mo Chutu from Rahan").[4]

His foundation at Lismore flourished after his lifetime, eclipsing the reputation of the saint's earlier church. It was able to withstand the Viking depredations which plagued the area and benefited from the generosity of Munster kings, notably the Mac Carthaig of Desmond.[4] In the 12th century, St Déclán's foundation of Ardmore aspired to the status of episcopal see in the new diocese, but the privilege went instead to Lismore.[4]